Disclosure: I build Schemity, a desktop ERD tool - this post is from our blog and uses it for the examples.
TL;DR: PNG and JPEG exports of a schema diagram have a fixed resolution, so they blur the moment someone zooms in, and large diagrams get cropped or produce enormous files. Schemity exports SVG - vector output that stays sharp at every zoom level - or a Mermaid erDiagram file that GitHub, GitLab, and Notion render natively, and lets you export a focused context view instead of the whole diagram, so the reader gets a crisp image scoped to what they actually need.
The fix for blurry schema diagram exports is not a higher DPI setting - it is exporting a vector format, and exporting less diagram. Schemity does both: SVG export that stays sharp at any zoom, and context views that let you export the ten tables your reader cares about instead of the two hundred they do not. And where the destination renders Mermaid - GitHub, GitLab, Notion - it exports the diagram as a Mermaid erDiagram file and skips the image entirely.
But start with the moment the problem shows up, because it never shows up on your screen. It shows up on someone else's. You finish arranging the diagram, export a PNG, paste it into the design doc, and move on. A day later a teammate opens the doc, zooms in to read a column name, and finds mush - anti-aliased gray smudges where the field types used to be. The diagram was correct. The export threw its readability away.
